Celtics have openings in starting lineup

Monday

Al Horford, Kyrie Irving and Gordon Hayward are definites, but coach Brad Stevens has decisions to make on the two other spots.

(The first in a five-part series looking at the Celtics before the start of training camp next week.)

The first three players making up the starting lineup of the 2017-18 Celtics are easy to figure out. Al Horford plus newcomers Kyrie Irving and Gordon Hayward will obviously be counted on heavily by coach Brad Stevens.

The other two spots are up for grabs as the Celtics head into training camp, which starts on Sept. 26 in Newport, R.I.

Horford will be in the front court for a second straight season with the Celtics, Irving takes over at point guard for Isaiah Thomas and free-agent signee Hayward will be on the wing.

There are several candidates to join them in the new-look Celtics lineup when the regular season gets going on Oct. 17 in Cleveland against the Cavaliers.

Jaylen Brown, about to enter his second season, Marcus Smart, Marcus Morris, Aron Baynes and perhaps even Terry Rozier would seem to be the five candidates to fill the last two starting spots.

Stevens has only three weeks of camp and four preseason games to find the right mix before the opener.

“The good news about our opportunity is we get a chance to go to work,’’ said Stevens during an introductory press conference for Irving and Hayward on Sept. 1. “We should be excited about our opportunities ahead. We’ve got a lot of good players in the room. We’re all going to have to find out what role we can play in order to help us get better.’’

Stevens went with a unit of Thomas, Avery Bradley, Jae Crowder, Horford and Amir Johnson when they were all healthy last season.

Now, Thomas and Crowder are with the Cavaliers, Bradley plays for the Detroit Pistons and Johnson signed with the Philadelphia 76ers.

Smart is a possibility to play opposite Irving in the backcourt, though he has been more effective coming off the bench and providing energy.

He is far from a pure shooting guard but has improved at the point and is the Celtics’ top defender.

Stevens may keep Smart in a reserve role and allow Irving to play off the ball later in games.

Rozier is another potential starter at a guard spot, though he will need to keep improving in order to make that happen.

There has been potential on display from Rozier during his two seasons, but flaws have to be corrected before his minutes take a leap.

Brown is going to be asked to do a lot more in his second season after he kept getting better as a rookie.

The Celtics could use him at forward or shooting guard since Stevens’ system can be position-less.

Brown showed he had much to learn as a first-year player, but there is so much potential there, and Stevens is going to boost his playing time.

Morris, acquired from the Pistons in the Bradley trade, might be the one to play in the front court with Horford. He would bring toughness and is a capable scorer.

Rebounding is again going to be an issue for the Celtics, so Stevens may elect to start the 6-foot-10 Baynes, who has been a starter just 24 games in five seasons.

He wouldn’t play a lot of minutes, but Baynes could help set a physical tone at the beginning of games and allow Horford to start off at power forward.

Another possibility is veteran center Andrew Bogut, who remains unsigned and could land with the Celtics, who have one roster opening, this week.

The seven-footer, who turns 33 in November, fractured his leg in his first game with the Cavaliers last March but is ready to resume basketball activity.